1. Field of the Invention
The invention concerns a yarn breakage stop motion device for textile machines, particularly tufting machines, consisting of a number of plates corresponding to the number of the yarns to be monitored. The plates are equipped with an eye on both ends, one which serves to guide a yarn to be monitored and the other to place the plate on a carrier axle. The plurality of plates together form a register in the pivoting range whereof a photocell acting on the drive mechanism of the machine is arranged.
2. Background of the Prior Art
In a known type of a yarn breakage stop motion device, the plates are aligned freely on the carrier axle, so that they are not only essentially freely displaceable in the lateral direction, but are also free to tilt within a range determined by the unavoidable manufacturing tolerances of the guide axle and the eye of the plate. In another known type of a yarn breakage stop motion device, the plates are guided in a grooved rail consisting essentially of a square strip into which guide slots are machined with a predetermined spacing in widths corresponding to the thickness of the plates and parallel to each other. The rail additionally provides a longitudinal bore in the area of the webs formed by the machining operation. The bore has a diameter corresponding to that of the eye to receive the carrier axle.
Both known yarn breakage stop motion devices have certain significant disadvantages. One of the essential disadvantages consists of the substantial installation effort required in the case of the removal or insertion of one or several plates into the register. For example, during damage or the resetting of the machine for a product with a different yarn distribution the plates frequently require removal or additional plates need to be inserted. In such a case, it is necessary initially to disassemble the entire register, followed by the removal of all of the plates unilaterally from the terminal plate to the damaged plate. In case of a comb register, this is done after first retracting the guide axle for the register. The insertion of the replacement plates follows and then reassembly of the register using the plates previously removed is required. Resetting of the machine by installing the register and threading the previously pulled yarn then comprises the final step.
The same effort is required in the case of a reequipment of the machine. The only difference is that in this instance, depending on the type of resetting for a product with a higher or lower yarn division instead of replacing a plate, the removal or addition of a plate or several plates is required.
The second primary disadvantage of the known yarn breakage stop motion device is that they do not permit the setting or maintenance of an accurately defined yarn tension. The further consequence of this disadvantage is that the monitoring of machines so adjusted is not possible, for example, for the production of tufted, looped fabric with a yarn breakage stop motion device. It is known that that the production of tufted, looped or boucle fabrics is effected in a manner wherein the yarn needled through the basic fabric is held by a gripper during the pulling of the needle in order to form a loop with only the loop that is formed being held to the point in time wherein the needle reaches its upper dead center and is then released. As a precondition of the application of a yarn breakage stop motion device in machines equipped in this manner, it is again necessary to adjust the drop weight of the plates with high accuracy to a low value and to maintain this value permanently. This is required in order to safely prevent the pulling of the loop just formed under the weight of the plate. The known yarn breakage stop motion devices do not permit such an accurate weight adjustment.